Mineralogy and geochemistry of ash and slag from coal gasification in China: a review

Li, Shuqin; Qi, Chuan; Jiang, Zhe; Zhang, Yanjun; Niu, Maofei; Li, Yuanyuan; Dai, Shifeng; Finkelman, Robert B.

doi:10.1080/00206814.2017.1287013

Cited by 49 publications

(23 citation statements)

References 37 publications

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“…This treatment not only occupies land resources, causes enormous environmental pressure, but also brings high transportation and processing costs to the enterprise. Therefore, it is especially important to realize the "zero emission" [9] of coal gasification technology and to find ways to recycle CGS.…”

Section: Introductionmentioning

confidence: 99%

“…At present, there are many researches on the resource utilization of fly ash and slag in the world [7,8,10]. However, since the CGS is obtained in a high-pressure vaporization furnace under a reducing atmosphere (CO, H 2 ) and 1400-1500 • C, its structure and composition are greatly different from those of fly ash and slag [3,5,9]. Therefore, it is difficult to realize the utilization of CGS by the same method.…”

Section: Introductionmentioning

confidence: 99%

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Green Synthesis Method and Application of NaP Zeolite Prepared by Coal Gasification Coarse Slag from Ningdong, China

Zhang

Zhao

et al. 2020

Applied Sciences

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In view of the current and urgent environmental protection needs, the use of industrial solid waste in China’s Ningdong is becoming more and more important. In this paper, NaP zeolite with good physical properties is synthesized by using coal gasification coarse slag (CGCS) as the raw material, without the addition of a silicon and aluminum source, without the addition of a template agent, and without high-temperature calcination. Add a small amount of NaOH and deionized water to the CGCS to adjust the molar ratio to SiO2:Al2O3:Na2O:H2O = 5.2:1.0:5.0:100. The effects of aging time, crystallization temperature, and crystallization time parameters on synthetic zeolite were studied. The raw materials and the obtained zeolite were tested by XRF, XRD, SEM, FT-IR, TG-DSC, BET, and other technologies. The results show that the specific surface area of the synthesized NaP zeolite can reach 161.06 m2/g, which has the characteristics of large specific surface area, regular morphology, and high crystallinity. We obtained NaP zeolite through a simple and low-cost synthesis method. The synthesized NaP zeolite was used to simulate the removal of ammonia nitrogen in wastewater, and the optimal removal rate was 92.67%. Among them, Na+ plays an important role in the synthesis of NaP zeolite and ion exchange with NH4+. Our research provides new ideas for solving the large-scale accumulation of CGCS and treating ammonia nitrogen in industrial wastewater. Thus, it is a promising green environmental protection and “treating waste by waste” route.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Green Synthesis Method and Application of NaP Zeolite Prepared by Coal Gasification Coarse Slag from Ningdong, China

Zhang

Zhao

et al. 2020

Applied Sciences

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“…During the oxidation process, oldhamite is first transformed into CaSO 4 , and then CaSO 4 is converted into CaO. Finally, CaO reacts with Al 2 O 3 and SiO 2 to produce gehlenite (Ca 2 Al 2 SiO 7 ) at 1100 • C [42][43][44][45]. When the temperature increases to 1400 • C, gehlenite is transformed to the thermodynamically stable anorthite (CaAl 2 Si 2 O 8 ).…”

Section: Mineral Transformation During Residual-coke Oxidation Processmentioning

confidence: 99%

Calcium-Bearing Minerals Transformation during Underground Coal Gasification

Liu

2019

Minerals

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Calcium‐bearing minerals are one of the main typical minerals in coal and coal ash. In the process of coal thermal conversion, calcium‐bearing minerals undergo different morphological transformation in which the reaction temperature, pressure, and atmosphere are important factors affecting their transformation. The reaction process of underground coal gasification (UCG) could be clearly divided into pyrolysis, reduction, and oxidation and the typical calcium‐bearing minerals are expected to indicate the actual reaction conditions of UCG. A high‐calcium coal, Zhundong coal, was used in this research. The products of UCG were prepared and the minerals were identified by X‐ray diffraction (XRD) and a scanning electron microscope coupled with an energy‐dispersive spectrometer (SEM‐EDS). The thermodynamic calculation was used to assist in understanding the transformation behaviors of calcium‐bearing minerals. The experimental results show that the calcium‐bearing mineral is gradually converted from gypsum (CaSO4·2H2O) in the raw coal into anhydrite (CaSO4) during the pyrolysis process. In the reduction stage, anhydrite reacts with the reducing gas (CO) to produce oldhamite (CaS), and the oldhamite is stably present in the reduction ash. During the oxidation process, oldhamite is first transformed into CaSO4, and then CaSO4 is converted into CaO. Finally, CaO reacts with Al2O3 and SiO2 to produce gehlenite (Ca2Al2SiO7) at 1100 °C. As the oxidation temperature rises to 1400 °C, gehlenite is transformed into the thermodynamically stable anorthite (CaAl2Si2O8). With the further progress of the reaction, anorthite will co‐melt with iron‐bearing minerals above 1500 °C. The ternary phase diagram of SiO2–Al2O3–CaO system proves that anorthite and gehlenite are the typical high‐temperature calcium‐bearing minerals when the mole fraction of SiO2 is higher than 0.6. Moreover, the gehlenite is converted to anorthite with the temperature rise, which is consistent with experimental results. This study provides a scientific basis for understanding the UCG reaction conditions.

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“…In 2018, coal consumption reached 2.7 billion tons [2], or about 1.9 billion tons of oil equivalent (1 ton of oil is equivalent to 1.43 tons of standard coal), accounting for 50.58% of global coal consumption. According to the China's 13th five-year plan (2016-2020) for National Economic and Social Development, China plans to cap coal consumption at 4.1 billion tons by 2020 [3], which implies coal consumption will rise sequentially [4][5][6]. The use of coal resources promotes economic development, meanwhile, air pollutants, particulate matter, as well as CCPs from coal combustion cause serious environmental problems [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Mineralogical and Environmental Geochemistry of Coal Combustion Products from Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, Northwest China

Zhuang

et al. 2019

Minerals

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The mineralogical and geochemical characteristics of feed coals and coal combustion products (CCPs) from the Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, were studied by means of proximate analysis, Power X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray analyzer (SEM-EDX), inductively coupled plasma atomic emission spectrometry (ICP-MS) and inductively coupled plasma mass spectrometry (ICP-AES). The environmental geochemistry of CCPs was evaluated by Al-normalized enrichment factor as well as European Standard EN-12457 leaching test. Two feed coals have the characteristics of low sulfur content, medium to high volatiles matter yields, medium moisture content, super low to medium ash yield, medium to high calorific value and low mineral content. The main crystalline facies in fly ash and slag are quartz and mullite, with a small amount of calcite, and some unburned carbon. Hematite, SrSO4 and barite also can be observed in fly ashes by SEM. Typical plerophere occurs in fine fly ash rather than the coarse fly ash. The concentration of most trace elements in CCPs falls within the lower concentration range of European fly ashes. With respect to the partitioning behavior of trace elements during coal combustion, S is highly volatile, and Mg, Na, Zn, B, Co, As, Nb, Zr, Cu and K also show certain volatility, which may to some extent emit to the atmosphere. Furthermore, leaching experiments show that leachable concentrations of most of the potentially toxic elements in CCPs are low, and the CCPs fall in the range between inert and nonhazardous landfill material regulated by the 2003/33/EC Decision.

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Mineralogy and geochemistry of ash and slag from coal gasification in China: a review

Cited by 49 publications

References 37 publications

Green Synthesis Method and Application of NaP Zeolite Prepared by Coal Gasification Coarse Slag from Ningdong, China

Green Synthesis Method and Application of NaP Zeolite Prepared by Coal Gasification Coarse Slag from Ningdong, China

Calcium-Bearing Minerals Transformation during Underground Coal Gasification

Mineralogical and Environmental Geochemistry of Coal Combustion Products from Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, Northwest China

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